DVD
DVD was originally an abbreviation for Digital Video Disk, however it was subsequently given the backronym Digital Versatile Disk due to the numerous purposes to which the medium could be put.
Essentially a high-density version of CD, the DVD format is available with either one or two sides, each of which may contain either one or two layers. Each layer holds around 4.7 GB of data, which gives the maximum capacity (double-sided, double-layered) of around 17 GB. Most commercial DVDs are single-sided and both single and double layered versions are common.
Hardware Issues Before considering the purchase of a DVD burner, you should consult sites that do reviews on DVD drives. Some drives, while compliant to standards may have problems writing certain DVD's at published speeds. Find a DVD burner that is fully supported by your Linux distribution and has a good report from users as to the quality and usability of the drive.
Playing DVDs under Linux
To play DVDs with (or without) menus under Linux use VLC
Manual Configuration
In order to correctly play DVD videos, DMA support needs to be enabled, and the libdvdcss library needs to be installed.
To enable DMA support, use the hdparm command:
# su (password) # hdparm /dev/dvd (view settings for dvd player) # hdparm -d1 /dev/dvd (turn on DMA support)
In situations when a is a "combo drive" and does both (1) play DVDs and (2) record CDs, it helps to separate the ide-cd module from ide-scsi, though, it's possible to do both at the same time. For this separation to work, sometimes it's necessary to remove "hdX = ide-scsi" from the boot loader as well. For instance, the following would switch from CD Writer to DVD Player.
# rmmod ide-scsi # modprobe ide-cd
Writable flavours
There are various types of writable DVD discs available.
- write-once formats (DVD+R, DVD-R)
- rewritable (DVD+RW, DVD-RW, DVD-RAM)
Generally the R/RW media has a capacity of 4.7GB.
The "+" and "-" versions are competing standards, each of which is backed by a number of large corporations. The key difference between the two is the more accurate addressing information on the "+" format, which allows the media to be written to in a true random-access method rather than in the contiguous "sessions" required by the "-" formats (and rewritable CDs). Neither the "-" nor "+" formats are universally playable in legacy DVD-ROM drives.
DVD-RAM is a different technology and needs a DVD drive labelled with the DVD-RAM logo. See separate article.
Writing DVDs under Linux
Write DVDs under Linux using k3b.
Data recovery
Data from a damaged disc can be recovered using the ddrescue utility, for example:
ddrescue /dev/sr0 recovered_image.img recovered_image.log
The tool saves its progress in the log file. Creating a log file is optional but it is necessary for resuming instead of starting over.
A command that might speed up the recovery process is:
sdparm --set=RRC=0 /dev/sr0
"RRC" refers to the "read retry count". Setting it to zero will cause the drive to get less stuck on errors.